Rootstocks for grapevines may contribute to scion vigor and winter hardiness, and may affect crop yield and composition. In an 8-year study of winegrape cultivar St. Pepin grafted onto five rootstocks ('St. Pepin', ES 15-53, MN 1065, MN Rip 64, C 3309), winter hardiness, vine vigor, yield, and fruit composition were measured. Weight of cane prunings, yield, and berry weight, cane periderm development, survival of buds in controlled freezing conditions, and fruit pH, titratable acidity and degrees Brix were measured. There were few significant differences in vine growth, yield and fruit composition among the rootstock-scion combinations. However, the most marked difference among the rootstock-scion combinations was the relationship of vine vigor and yield. St Pepin grafted onto MN Rip 64 had low vigor but high yields in contrast to C3309 which had high vigor and high yields and MN 1065 which had low vigor and low yields.